Perfect recipe for a storm

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We can't keep making greenhouse gases and playing
Russian roulette with the world's climate, writes Michael
Molitor.

Jurgen Trittin, the German Environment Minister, has just
claimed that hurricane Katrina was caused by global warming. The
devastating impact of Katrina has ignited, once again, the
scientific and political debate about whether the growth in damage
from extreme weather events is being driven by human modification
of the global climate system (what is commonly referred to as
"global warming") or if it results simply as a function of natural
changes in the weather. Do emissions of greenhouse gases at
coal-fired power plants in Victoria have anything to do with the
occurrence or ferocity of a large hurricane striking the Gulf Coast
of the United States? Supercomputer models of the global climate
system using increasing detail and sophistication have long since
made the connection between the addition of greenhouse gases into
the atmosphere by humans and the increased frequency and intensity
of extreme weather events (droughts, tornadoes, hurricanes,
cyclones, etc). The theory to explain this relationship is well
understood - locating hard empirical evidence is proving more
difficult.

Our understanding of the climate system, and the ways in which
it is being modified by human activity, is not sufficiently robust
to tell us whether any specific extreme weather event was caused or
influenced by human activity. Although it may not be possible to
make a concrete link between cause and effect today, it is my view
that in the near future evolving developments in climate science
will demonstrate that both the probability and power behind Katrina
were influenced by human activities. Basic rules of physics tell us
that if humans load the atmosphere with more greenhouse gases
(largely through the combustion of fossil fuels), and those gases
trap more of the sun's heat, then ocean surface temperatures will
rise. It is the heat stored in the surface waters of the oceans in
the tropics that provides the key source of energy that drives
hurricanes (or typhoons and cyclones, depending on your
location).

Katrina provides an important opportunity to learn other
valuable lessons if we move away from questions about the human
influence on climate that remain, at least for now, unanswerable.
First, as human populations grow in number and in affluence we are
placing more and more people at risk of extreme weather events.
There has been a substantial growth in the number of people living
in homes of increasing size and value that are now in the path of
potential hurricanes and other extreme weather events.

Insurance and re-insurance companies have already begun the
process of adjusting insurance premiums to reflect these risks.
Policymakers need to rethink their approach to permitting more and
more homes and apartments to be built on, for example, coastal land
at risk of flooding and other damage from extreme weather
events.

Australians have only to think back to Christmas Eve 1974 to
remember the devastating impact of cyclone Tracy. The computer
models, and recent short-term empirical evidence, would seem to
suggest that extreme weather events and their consequences (water
shortages, flooding, heat waves, bushfires) will increase in
Australia as well as elsewhere in the world. Of greater
significance to Australians are possible changes to the climate
system that will create even more problems for the availability of
fresh water - possibly the key limiting factor to growth in
Australia in the near to medium term.

Although Australia is at significant risk from a climate system
modified by human activity, Australians are the highest emitters of
greenhouse gases in the world at about 27 tonnes of carbon dioxide
per person per year (the global average is about 5 tonnes of carbon
dioxide per person per year). Furthermore, Australia's economy is
strongly supported by the use and export of products that emit a
large amount of greenhouse gases either when produced (e.g.
aluminium) or when used (e.g. energy coal and coking coal).

The Katrina disaster should remind us that it is absurd for
humanity to continue to emit 30 gigatonnes (30,000,000,000 metric
tonnes) of carbon dioxide every year and simply hope that this will
have little or no impact on the climate system. We need to rapidly
and dramatically reduce our emissions of greenhouse gases into the
atmosphere to stop playing Russian roulette with the climate
system. Concentrations in the atmosphere of carbon dioxide, the key
greenhouse gas, are about 380 parts per million; they were only 290
ppm in the year 1850. If we attempt to stabilise concentrations at
500 ppm by the year 2100, a level many scientists believe is the
highest we can tolerate without putting humanity at unacceptable
levels of risk, then we will need to find ways of avoiding 640
gigatonnes of carbon dioxide emissions that will occur under
"business as usual" conditions in the next 50 years. This will
require a gigantic global effort to wean people off their growing
high-carbon, high energy diets in both the developed world (e.g.
Australia and the United States) as well as in the developing world
(e.g. China and India).

Finally, Katrina sends us the most chilling message of all; the
storm makes it clear that everyone on this planet is at risk from
climate change - regardless of your economic status or geographic
location. Katrina did not spare the homes of wealthy people or the
staggeringly expensive offshore oil drilling platforms in the Gulf
of Mexico. The damage and impact of Katrina will be felt worldwide
(for example, through increases in the prices of oil and gas) - we
can only hope that political leaders will recognise the important
global lessons she has delivered.

Dr Michael Molitor is the chief executive of ClimateWEDGE
Ltd, and the former global leader of the climate change services
team at PricewaterhouseCoopers.